Transport Dynamics of the Northeast Pacific In a Changing Climate

Over the last decades, the Northeast Pacific (NEP), has experienced dramatic changes in its climate with the occurrence of a sequence of record-breaking temperature extremes between 2013-2019, such as the multi-year 2013-15 Northeast Pacific marine heatwave, the strong 2015-16 El Niño, and more recently the ongoing 2019 Alaskan heatwave. The resulting changes in temperature and eddy-scale ocean transport dynamics (e.g. cross-shore, alongshore, upwelling) in the Gulf of Alaska (GOA) and California Current System (CCS) led to dramatic ecosystem impacts that include harmful algal blooms along the coasts, low primary productivity, massive die offs of mammals and birds. Despite advances in our understanding of the large-scale Pacific changes, it remains unclear how regional transport dynamics of the GOA and CCS are responding to the observed climate extremes and trends in decadal climate variability in the NEP, and what changes in transport statistics are expected under anthropogenic climate forcing. Key Questions: (Q1) How did the amplification of the regional climate variance in the Northeast Pacific over the last decades impact eddy-scale transport dynamics (e.g. alongshore, cross-shore, upwelling) in the California and Gulf of Alaska circulation systems? (Q2) What are the Pacific largescale drivers that control the regional ocean transport statistics during the recent temperature extremes (2013-2019), and are the changes in transport significant (e.g. an extreme) in the context of historical long-term variability (1950-2000)? (Q3) How are ecologically-relevant transport statistics in the Northeast Pacific expected to change under anthropogenic forcing (2050-2100), and are these changes consistent with what occurred during the recent extremes (2013-2019)? The goal of this research is to identify and estimate the response of ecologically-relevant eddyscale transport dynamics in the Northeast Pacific to (GOAL1) recent amplifications of large-scale climate forcing (e.g. extremes, trends, decadal variability), and (GOAL2) projected changes in anthropogenic climate change as inferred from large-ensemble of individual Earth System Models (ESMs) that allow to separate the internal vs forced variability. Two female Ph.D. students will be trained and mentored. The PI will share this research in his ongoing interdisciplinary research/leadership activities in the California-LTER, PICES, and US CLIVAR. The high-resolution regional climate ensemble archive generated in this study will be a unique asset to the marine research community in the Northeast Pacific. The PI will work with the CCE-LTER team to make the model output available for interdisciplinary studies and to develop a set of Linear Inverse Model tutorials to help marine ecosystem scientists apply this methodology to explore ecological dynamics. The approaches & TASKs of the investigation will include (T1) a 10-member ensemble of high-resolution regional coupled ocean-atmosphere model historical simulations of the Northeast Pacific (1950-2019) with a passive tracers transport module to downscale the impact of large-scale Pacific climate forcing on regional transport dynamics in the GOA and CCS, (T2) a set of Linear Inverse Models (LIMs) to identify and quantify the effects of large-scale drivers on ecologically-relevant regional transport statistics inferred from the passive tracers, (T3) the use of large ensemble simulations of individual ESMs (e.g. CESM, GFDL ESM2M) under the SSP5-8.5 or equivalent scenario as input to the LIM to investigate how anthropogenic forcing is projected to impact the targeted transport statistics in the context of internal climate variability. The recent increase in climate variance and ecosystem synchrony in the Northeast Pacific, together with the ecological and societal impacts of the temperatures extremes of the 2013-15 Northeast Pacific marine heatwave, the strong 2015-16 El Niño, 2019 Alaskan heatwave, raise concern and questions of the role of natural and anthropogenic forcing in the regional oceanography of the Northeast Pacific. Eddy-scale transport dynamics (e.g. alongshore, cross-shore, upwelling) have long been recognized as a key driver of marine ecosystem change, yet the response of these dynamics to a changing climate remains unclear. This work will provide understanding on how the recent trends in the climate variance of ecological drivers relates to long-term historical variability and to anthropogenic forcing. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.